U.S. patent application number 13/407343 was filed with the patent office on 2013-08-29 for efficiency heating, ventilating, and air-conditioning through extended run-time control.
The applicant listed for this patent is Joseph E. Childs, Robert J. Cox, Roger W. Rognli, Brock Simonson. Invention is credited to Joseph E. Childs, Robert J. Cox, Roger W. Rognli, Brock Simonson.
Application Number | 20130219931 13/407343 |
Document ID | / |
Family ID | 49001351 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130219931 |
Kind Code |
A1 |
Childs; Joseph E. ; et
al. |
August 29, 2013 |
EFFICIENCY HEATING, VENTILATING, AND AIR-CONDITIONING THROUGH
EXTENDED RUN-TIME CONTROL
Abstract
An extended run time device for extending the time that a
compressor-based heating, ventilating, and air-conditioning (HVAC)
system runs so as to increase energy efficiency of the HVAC system.
The extended run time device includes a sensing circuit, a
switching device and a processor. Based upon a signal from the
sensing circuit, the processor causes the switching device to
transmit a proxy control signal to the compressor, thereby causing
power to the compressor to be maintained for a time period longer
than a time period requested by the temperature control device.
Inventors: |
Childs; Joseph E.; (Golden,
CO) ; Rognli; Roger W.; (Otsego, MN) ; Cox;
Robert J.; (Maple Grove, MN) ; Simonson; Brock;
(Carrington, ND) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Childs; Joseph E.
Rognli; Roger W.
Cox; Robert J.
Simonson; Brock |
Golden
Otsego
Maple Grove
Carrington |
CO
MN
MN
ND |
US
US
US
US |
|
|
Family ID: |
49001351 |
Appl. No.: |
13/407343 |
Filed: |
February 28, 2012 |
Current U.S.
Class: |
62/115 ;
62/126 |
Current CPC
Class: |
F24F 11/61 20180101;
F25B 2600/02 20130101; F24F 11/46 20180101; F25B 2600/01 20130101;
F24F 11/83 20180101; F25B 2600/024 20130101; F25B 49/022 20130101;
F25B 2600/0251 20130101; F25B 2600/25 20130101 |
Class at
Publication: |
62/115 ;
62/126 |
International
Class: |
F25B 49/02 20060101
F25B049/02; F25B 1/00 20060101 F25B001/00 |
Claims
1. An extended run time device for extending the time that a
compressor-based heating, ventilating, and air-conditioning (HVAC)
system runs so as to increase energy efficiency of the HVAC system,
the extended run time device comprising: a sensing circuit adapted
to receive a call-for-cool control signal from a temperature
control device and to output a sense signal; a compressor
time-extending switching device having a first terminal, a second
terminal, and a third terminal, the first terminal adapted to
electrically connect to a control circuit that controls electrical
power to a compressor of an HVAC system, the second terminal
adapted to receive the call-for-cool control signal, and the third
terminal adapted to receive a proxy call-for-cool control signal,
the compressor time-extending switching device configured to
selectively connect the first terminal to the second terminal,
thereby causing the control circuit to receive the call-for-cool
control signal, or to connect the first terminal to the third
terminal, thereby causing the control circuit to receive the proxy
call-for-cool signal; and a processor in electrical communication
with the sensing circuit and the compressor time-extending
switching device, the processor adapted to receive the sense signal
from the sensing circuit, determine a requested compressor run time
based upon the call-for-cool signal, and to transmit a switching
control signal to the compressor time-extending switching device,
thereby controlling the compressor time-extending switching device;
wherein when the requested compressor run time is less than a
predetermined minimum compressor run time, the processor transmits
the switching control signal to the compressor time-extending
switching device, causing the compressor time-extending switching
device to disconnect the first terminal from the second terminal,
and to connect the first terminal to the third terminal, thereby
causing the control circuit to receive the proxy call-for-cool
control signal and to maintain electrical power to the compressor
for an extended run time period.
2. The extended run-time device of claim 1, wherein the temperature
control device comprises a thermostat.
3. The extended run-time device of claim 1, wherein the sensing
circuit samples the call-for-cool control signal at a predetermined
sampling frequency to detect the presence or absence of a
call-for-cool control voltage.
4. The extended run-time device of claim 1, wherein the
call-for-cool control signal comprises a 24VAC control signal.
5. The extended run-time device of claim 1, wherein the sensing
circuit comprises a Schmitt trigger sense circuit.
6. The extended run-time device of claim 1, wherein the compressor
time-extending switching device comprises a relay.
7. The extended run-time device of claim 1, wherein the proxy
call-for-cool signal is supplied by a power supply in electrical
communication with the third terminal of the compressor
time-extending switching device, and the proxy call-for-cool signal
includes substantially the same electrical characteristics as the
call-for-cool control signal.
8. The extended run-time device of claim 1, wherein the processor
is further configured to determine whether the requested compressor
run time is less than a predetermined minimum compressor run time,
and to transmit the switching control signal to the compressor
time-extending switching device when the compressor run time is
less than the predetermined minimum compressor run time.
9. The extended run-time device of claim 1, wherein the extended
compressor run time period is substantially equal to the minimum
compressor run-time period less the requested compressor run time
period.
10. The extended run-time device of claim 1, wherein the extended
compressor run time period is a multiple of the requested run time
period.
11. The extended run-time device of claim 1, further comprising a
fan time-extending switching device in electrical communication
with the temperature control device, a circulation fan, and the
processor.
12. The extended run-time device of claim 11, wherein the processor
controls the fan time-extending switching device so as to extend a
requested call-for-fan time period from the temperature control
device, thereby causing the circulation fan to continue to run
after an expiration of the requested call-for-fan time period.
13. The extended run-time device of claim 11, wherein the control
circuit comprises a cooling contactor.
14. The extended run-time device of claim 1, wherein the extended
run-time device is integrated into a load-control switch.
15. The extended run-time device of claim 1, wherein the extended
run-time device is integrated into a fan-control board of a forced
air unit.
16. A method of improving energy efficiency of a heating,
ventilating, and air-conditioning (HVAC) system that includes a
temperature control device in communication with a compressor, a
circulation fan, the method comprising: monitoring a call-for-cool
control signal of a temperature control device, the call-for-cool
control signal causing power to be applied to a compressor of an
HVAC system for a requested compressor run-time period; determining
the duration of the requested compressor run-time period of the
temperature control device; and causing power to the compressor to
be maintained for an extended compressor run-time period when the
duration of the requested compressor run time period is less than a
predetermined minimum run time period, the extended compressor run
time period commencing after an expiration of the requested
compressor run time period such that the compressor is powered for
a total run time period that is greater than the requested
compressor run-time period, thereby increasing an energy efficiency
of the HVAC system.
17. The method of claim 16, wherein monitoring a call-for-cool
signal comprises sampling a signal line carrying the call-for-cool
control signal using a sensing circuit.
18. The method of claim 16, wherein the call-for-cool control
signal comprises a 24VAC control signal transmitted from a terminal
of the temperature control device.
19. The method of claim 16, wherein causing power to be applied to
a compressor of the HVAC system for a requested compressor run-time
period comprises transmitting the call-for-cool control signal to a
contactor of the compressor, thereby causing the contactor to
connect the compressor to a power source.
20. The method of claim 16, wherein causing power to the compressor
to be maintained for an extended run-time period comprises
transmitting a proxy call-for-cool control signal to a contactor of
the compressor, thereby causing the contactor to maintain a
connection of the compressor to a power source.
21. The method of claim 16, further comprising determining the
extended compressor run-time period.
22. The method of claim 21, wherein determining the extended
run-time period comprises a processor setting the extended run-time
period to be substantially equal to the requested run-time period
multiplied by a multiplier M.
23. The method of claim 22, wherein the multiplier M is a
predetermined, fixed value.
24. The method of claim 22, wherein the multiplier M is dynamically
determined based upon the requested compressor run-time period.
25. The method of claim 24, wherein the multiplier M is dynamically
determined based upon the requested compressor run-time period and
the predetermined minimum compressor run time.
26. The method of claim 16, further comprising causing power to a
circulation fan to be maintained for a time period greater than or
equal to the extended compressor run-time period, the time period
commencing after an expiration of a requested fan run time period,
thereby causing the circulation fan to be powered for at least as
long as the compressor is powered.
27. An extended run time device for extending the time that a
compressor-based heating, ventilating, and air-conditioning (HVAC)
system runs so as to increase energy efficiency of the HVAC system,
the extended run time device comprising: means for monitoring a
call-for-cool control signal of a temperature control device, the
call-for-cool control signal causing power to be applied to a
compressor of the HVAC system for a requested run-time period;
means for determining the duration of the requested run-time period
of the temperature control device; and means for causing power to
the compressor to be maintained for an extended run-time period
when the duration of the requested run time period is less than a
predetermined minimum run time period, the extended run time period
commencing after an expiration of the requested run time period
such that the compressor is powered for a total run time period
that is greater than the requested run-time period, thereby
increasing an energy efficiency of the HVAC system.
28. The extended run-time device of claim 27, wherein the means for
monitoring the call-for-cool control signal comprises means for
sampling a voltage of a control signal line in electrical
communication with the temperature control device.
29. The extended run-time device of claim 27, further comprising
means for determining the extended run-time period.
30. The extended run-time device of claim 27, further comprising
means for causing power to a circulation fan to be maintained for a
time period greater than or equal to the extended compressor
run-time period.
31. An improved-efficiency heating, ventilating and
air-conditioning (HVAC) system, comprising: a temperature control
device monitoring and controlling a space temperature of a premise
and transmitting a call-for-cool control signal; an outdoor unit
receiving the call-for-cool control signal transmitted from the
temperature control device, the outdoor unit including a compressor
and an electrical contactor for switching power on and off to the
compressor; and an extended run-time device in electrical
communication with the thermostat and the outdoor unit, the
extended run-time device receiving the call-for-cool control signal
and causing the electrical contactor of the outdoor unit to
maintain power to the compressor for an extended run-time period
after the temperature control device ceases to transmit the
call-for-cool control signal.
32. The system of claim 31, further comprising a circulation fan in
electrical communication with the temperature control device and
the extended run-time device, and wherein the extended run-time
device causes the circulation fan to continue operating after the
temperature control device ceases to transmit a call-for-fan
control signal.
33. The system of claim 31, wherein the extended run-time device
includes: a compressor extended-time switching device, a sensing
circuit adapted to detect the call-for-cool control signal, a
processor controlling the compressor extended-time switching device
and receiving a data signal from the sensing circuit; wherein the
processor is configured to determine a thermostat-requested
compressor run time based upon a duration of the call-for-cool
control signal, compare the thermostat-requested compressor run
time with a predetermined minimum compressor run time, and to cause
the compressor extended-time switching device to switch from
transmitting the call-for-cool control signal to the contactor to
transmitting an output of the power supply to the contactor,
thereby maintaining power to the compressor for an extended
run-time period after the temperature control device ceases to
transmit the call-for-cool control signal.
34. The system of claim 33, wherein the output of the power supply
comprises substantially the same voltage as the call-for-cool
control signal.
35. A load-control switch (LCS) for selectively powering an
electrical load of a heating, ventilating, and air-conditioning
(HVAC) system and improving the efficiency of the electrical load
through extending run-time operation of the load, the LCS
comprising: a transceiver configured to communicate with an
electrical utility over a communications network; an extended
run-time (ERT) device in electrical communication with the
transceiver, the ERT device including: a sensing circuit adapted to
receive a call-for-cool control signal from the temperature sensing
and controlling unit and to output a sense signal; a compressor
time-extending switching device having a first terminal, a second
terminal, and a third terminal, the first terminal adapted to
electrically connect to a control circuit that controls electrical
power to a compressor of an HVAC system, the second terminal
adapted to receive the call-for-cool control signal, and the third
terminal adapted to receive a proxy call-for-cool control signal,
the compressor time-extending switching device configured to
selectively connect the first terminal to the second terminal,
thereby causing the control circuit to receive the call-for-cool
control signal, or to connect the first terminal to the third
terminal, thereby causing the control circuit to receive the proxy
call-for-cool signal; and a processor in electrical communication
with the sensing circuit and the compressor time-extending
switching device, the processor adapted to receive the sense signal
from the sensing circuit, determine a requested compressor run time
based upon the call-for-cool signal, and to transmit a switching
control signal to the compressor time-extending switching device,
thereby controlling the compressor time-extending switching device;
wherein when the requested compressor run time is less than a
predetermined minimum compressor run time, the processor transmits
the switching control signal to the compressor time-extending
switching device, causing the compressor time-extending switching
device to disconnect the first terminal from the second terminal,
and to connect the first terminal to the third terminal, thereby
causing the control circuit to receive the proxy call-for-cool
control signal and to maintain electrical power to the compressor
for an extended run time period.
36. The extended run-time device of claim 35, wherein the sensing
circuit samples the call-for-cool control signal at a predetermined
sampling frequency to detect the presence or absence of a
call-for-cool control voltage.
37. The extended run-time device of claim 35, wherein the sensing
circuit comprises a Schmitt trigger sense circuit.
38. The extended run-time device of claim 35, wherein the
compressor time-extending switching device comprises a relay.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to improving energy
efficiency of heating, ventilating, and air-conditioning systems.
More particularly, the present invention relates to systems,
devices and methods for improving efficiencies of over-sized
heating, ventilating, and air-conditioning systems by controlling
and extending cyclical run times of the systems.
BACKGROUND OF THE INVENTION
[0002] Electric utilities need to match generation to load, or
supply to demand. Traditionally, this is done on the supply side
using Automation Generation Control (AGC). As loads are added to an
electricity grid and demand rises, utilities increase output of
existing generators to solve increases in demand. To solve the
issue of continuing long-term demand, utilities typically invest in
additional generators and plants to match rising demand. As load
levels fall, generator output to a certain extent may be reduced or
taken off line to match falling demand. As the overall demand for
electricity grows, the cost to add power plants and generation
equipment that serve only to fill peak demand becomes extremely
costly.
[0003] In response to the high cost of peaking plants, electric
utility companies have developed solutions and incentives aimed at
reducing both commercial and residential demand for electricity. In
the case of office buildings, factories and other commercial
buildings having relatively large-scale individual loads, utilities
incentivize owners with differential electricity rates to install
locally-controlled load-management systems that reduce on-site
demand. Reduction of any individual large scale loads by such a
load-management systems may significantly impact overall demand on
its connected grid.
[0004] In the case of individual residences having relatively
small-scale electrical loads, utilities incentivize some consumers
to allow installation of demand-response technology at the
residence to control high-usage appliances such as air-conditioning
(AC) compressors, water heaters, pool heaters, and so on. Such
technology aids the utilities in easing demand during sustained
periods of peak usage.
[0005] Demand-response technology used to manage
thermostatically-controlled loads such as AC compressors typically
consists of a demand-response thermostat or a load-control switch
(LCS) device. A demand-response thermostat generally controls
operation of a load by manipulating space temperature. An LCS
device can be wired into the power supply line of the AC compressor
or other electrical load, and thereby interrupt power to the load
when the load is to be controlled.
[0006] However, while the demand-response schemes described above
shed demand during peak times, especially for systems utilizing AC
units, that demand is often time-delayed and merely pushed to
another time along the utility demand timeline. In other words,
demand-response schemes are suitable for reducing peak loads, but
do not always affect an actual decrease in energy usage. A key
problem lies in the energy consumed by AC units typically used in
thermostatically-controlled HVAC systems. A majority of the energy
consumed by such a system is spent powering the AC compressor. In a
recent Environmental Protection Agency report, it was reported that
air conditioning accounts for 13% of total home energy expenses on
average, and over 20% in hot, humid regions. This statistic is made
more significant by the fact that AC units are typically used
between three to five months per year, so their effect on the peak
demand during summer periods is very significant.
[0007] An oversized AC unit exacerbates the problem of high-energy
consumption by HVAC systems. The accurate sizing of HVAC equipment,
and specifically, the AC unit, is often quite challenging. Many
factors contribute to the proper sizing of an AC unit, including
the angle at which the sun contacts the home, the type of windows
installed in the home, the interior window shading of the windows,
the insulation installed in the home, the air circulation patterns,
the efficiency of the duct system, and the size of the living
space, among others. In addition, those factors change over time as
the home and landscaping ages. Because those involved with home
construction or AC unit selection, like homeowners and
homebuilders, do not want to undersize an AC unit and have to
replace the unit later, AC units tend to be oversized.
Additionally, oversized units typically provide cooling more
quickly, thus avoiding any chance of not meeting the cooling demand
of the occupants.
[0008] However, the oversizing of AC units contributes to the
problem of energy overusage, among other issues. One problem is the
short run times of oversized units where the units run for shorter
periods of time than are engineered for optimum operation. The
efficiency of air conditioners is low when first starting, and
increases gradually, reaching peak efficiency in about 10 minutes
for most residential AC units. (e.g. long enough for the unit to be
running at optimum efficiency). In addition even a properly sized
unit will have short run times on days where cooling demand is
low.
[0009] A number of other problems arise because of short run times.
Relatively short operation times followed by relatively long off
times do not allow the HVAC system to effectively remove humidity.
Improperly dehumidified air adversely effects home comfort, reduces
AC cooling efficiency, and can also promote the growth of mold and
mildew indoors. Likewise, short run times decrease overall air
circulation, resulting in repercussions on air quality and home
comfort. Perhaps most importantly, short run times costs homeowners
and commercial building owners additional money to operate, as the
units are not operating at peak efficiency and reduction in overall
life of the unit because the number of AC unit cycles is directly
related to a units life (more than just runtime hours).
[0010] One attempt at improving the energy-efficiency
characteristics of HVAC systems relies on variable speed AC unit
compressors and fans that may be used to increase system turndown.
However, such technology remains relatively expensive for new HVAC
units. Further, retrofitting existing, working HVAC units to
replace "single speed" technology with variable speed technology
does not provide a convenient nor cost-effective solution for
improving energy efficiency.
[0011] Another attempt at improving AC system efficiency is
described in U.S. Pat. No. 5,960,639 to Hammer, entitled "Apparatus
for Regulating Compressor Cycles to Improve Air
Conditioning/Refrigeration Unit Efficiency". Hammer discloses
methods and systems for addressing compressor short-cycling.
Short-cycling occurs when the time between a compressor stopping
then restarting is so short that coolant pressures within the HVAC
system do not have time to equalize, and the compressor does not
have time to cool. Such conditions may occur in undersized HVAC
systems, and result in decreased system efficiency. While the
invention disclosed by Hammer addresses efficiencies for systems
experiencing short-cycling, often in undersized units, or on peak
usage days, Hammer fails to address the energy inefficiencies
caused by short run times (as opposed to short off times) occurring
in oversized AC systems.
[0012] Thus, there remains a need for technology capable of
reducing energy imposing efficiencies of existing, oversized HVAC
systems.
SUMMARY OF THE INVENTION
[0013] In an embodiment, the present invention comprises a run time
device for extending the time that a heating, ventilating, and
air-conditioning (HVAC) system runs so as to increase energy
efficiency of the HVAC system. The extended run time device
comprises: a sensing circuit adapted to receive a call-for-cool
control signal from a temperature control device and output a
control signal; a compressor time-extending switching device having
a first terminal, a second terminal, and a third terminal, the
first terminal adapted to electrically connect to a control
circuit, such as a cooling contactor, that controls electrical
power to a compressor of an HVAC system, the second terminal
adapted to receive the call-for-cool control signal, and the third
terminal adapted to receive a proxy call-for-cool control signal,
the compressor time-extending switching device configured to
selectively connect the first terminal to the second terminal,
thereby causing the control circuit to receive the call-for-cool
control signal, or to connect the first terminal to the third
terminal, thereby causing the control circuit to receive the proxy
call-for-cool signal; and a processor in electrical communication
with the sensing circuit and the compressor time-extending
switching device, the processor adapted to receive the sense signal
from the sensing circuit, determine a requested compressor run time
based upon the call-for-cool signal, and to transmit a switching
control signal to the compressor time-extending switching device,
thereby controlling the compressor time-extending switching device;
wherein when the requested compressor run time is less than a
predetermined minimum compressor run time, the processor transmits
the switching control signal to the compressor time-extending
switching device, causing the compressor time-extending switching
device to disconnect the first terminal from the second terminal,
and to connect the first terminal to the third terminal, thereby
causing the control circuit to receive the proxy call-for-cool
control signal such that the control circuit causes power to be
maintained to the compressor for an extended run time period.
[0014] In another embodiment, the present invention comprises a
method of improving energy efficiency of a heating, ventilating,
and air-conditioning (HVAC) system that includes a temperature
control device in communication with a compressor, and a
circulation fan. The method comprises: monitoring a call-for-cool
control signal of a temperature control device, the call-for-cool
control signal causing power to be applied to a compressor of an
HVAC system for a requested compressor run-time period; determining
the duration of the requested compressor run-time period of the
temperature control device; comparing the duration of the requested
run time period of the temperature control device to a
predetermined minimum run-time period; and causing power to the
compressor to be maintained for an extended compressor run-time
period when the duration of the requested compressor run time
period is less than the predetermined minimum run time period, the
extended compressor run time period commencing after an expiration
of the requested compressor run time period such that the
compressor is powered for a total run time period that is greater
than the requested compressor run-time period, thereby increasing
an energy efficiency of the HVAC system.
[0015] In another embodiment, the present invention comprises an
extended run time device for extending the time that a
compressor-based heating, ventilating, and air-conditioning (HVAC)
system runs so as to increase energy efficiency of the HVAC system.
The extended run time device comprises: means for monitoring a
call-for-cool control signal of a temperature control device, the
call-for-cool control signal causing power to be applied to a
compressor of the HVAC system for a requested run-time period;
means for determining the duration of the requested run-time period
of the temperature control device; means for comparing the duration
of the requested run time period of the temperature control device
to a predetermined minimum run-time period; and means for causing
power to the compressor to be maintained for an extended run-time
period when the duration of the requested run time period is less
than the predetermined minimum run time period, the extended run
time period commencing after an expiration of the requested run
time period such that the compressor is powered for a total run
time period that is greater than the requested run-time period,
thereby increasing an energy efficiency of the HVAC system.
[0016] In yet another embodiment, the present invention comprises
an improved-efficiency heating, ventilating and air-conditioning
(HVAC) system. The system comprises: a temperature control device
monitoring and controlling a space temperature of a premise and
transmitting a call-for-cool control signal; an outdoor unit
receiving the call-for-cool control signal transmitted from the
temperature control device, the outdoor unit including a compressor
and an electrical contactor for switching power on and off to the
compressor; and an extended run-time device in electrical
communication with the thermostat and the outdoor unit, the
extended run-time device receiving the call-for-cool control signal
and causing the electrical contactor of the outdoor unit to
maintain power to the compressor for an extended run-time period
after the temperature control device ceases to transmit the
call-for-cool control signal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The invention may be more completely understood in
consideration of the following detailed description of various
embodiments of the invention in connection with the accompanying
drawings, in which:
[0018] FIG. 1 is a diagram of a premise receiving electricity
through an electrical distribution network and having a heating,
ventilating, and air conditioning (HVAC) system with an extended
run-time (ERT) device, according to an embodiment of the present
invention;
[0019] FIG. 2 is an HVAC efficiency versus run time chart for an
exemplary HVAC system;
[0020] FIG. 3 is a block diagram of the HVAC system with the ERT
device of FIG. 1, in a pre-extension mode, according to an
embodiment of the present invention;
[0021] FIG. 4 is the block diagram of the HVAC system and ERT
device of FIG. 3, in an extension mode; and
[0022] FIG. 5 is a flow chart of a method of extending an HVAC
system run time for improving system energy efficiency, according
to an embodiment of the present invention.
[0023] While the invention is amenable to various modifications and
alternative forms, specifics thereof have been shown by way of
example in the drawings and will be described in detail. It should
be understood, however, that the intention is not to limit the
invention to the particular embodiments described. On the contrary,
the intention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the invention
as defined by the appended claims.
DETAILED DESCRIPTION
[0024] Referring to FIG. 1, improved-efficiency heating,
ventilating, and air-conditioning (HVAC) system 100 is depicted.
Improved-efficiency HVAC system 100 is located at premise 102 which
receives electricity from electrical utility provider 104.
[0025] Premise 102 though depicted as a residential building or
home, may also be a commercial building, industrial building, or
any such building or structure having an interior space requiring
heating or cooling. Though the term "HVAC" is generally understood
to mean "heating, ventilating, and air conditioning", it will be
understood that improved-efficiency HVAC system 100 may comprise
heating and cooling capability, just cooling capability, or just
heating capability. As such, when specific reference is made to a
cooling configuration and operation, it will be understood that the
same configuration and operation may exist and operate as a heating
configuration and operation.
[0026] Electrical utility provider 104 includes electricity
generation equipment 106 connected to electricity transmission and
distribution system 108. Electricity is generated by electricity
generation equipment 106 at electrical utility provider 104 and
transferred to premise 102 via electricity transmission and
distribution system 108. Actual electricity consumption at premise
102 may be measured by electricity meter 110.
[0027] Electricity meter 110 may be a standard non-communicative
device, or may be a "smart meter" tied into an Advanced Meter
Infrastructure (AMI) or an electricity "smart grid", capable of
communicating with electricity utility provider 104 over a
long-haul communication network (not depicted), and in some cases
capable of communicating with local devices a short-haul
communication network (not depicted) at or near premise 102.
[0028] Improved-efficiency HVAC system 100 includes temperature
control device 112, extended-run-time (ERT) device 114 of the
present invention, forced air unit (FAU) 116 with circulation fan
118, and outdoor unit 120 with compressor 122. Temperature control
device 112 is in electrical communication with ERT device 114 and
FAU 116; ERT device is in electrical communication with FAU 116 and
outdoor unit 120.
[0029] Temperature control device 112 may be any of a number of
known thermostats or temperature control devices used to regulate a
temperature of a space within premise 102. As such, temperature
control device 112 may be programmable, non-programmable, digital,
mechanical, communicative, and so on. Temperature control device
112 may operate on 24VAC, or another voltage as needed.
[0030] FAU 116 includes circulation fan 118, and may also include
electrical control circuitry having several electrical terminals,
as discussed further below. FAU 116 may be any of several known
types of forced air units used to condition and circulate air. FAU
116 may also include heating and cooling elements, filters,
dampers, and other related HVAC equipment not depicted. FAU 116 and
circulation fan 116 may be connected to ductwork for distributing
conditioned air to all or portions of premise 102.
[0031] Circulation fan 118 in an embodiment may be a single-speed
electric fan located within FAU 116, and turned on and off to move
air through premise 102. In other embodiments, circulation fan 124
may be a variable-speed or adjustable-speed fan controlled to vary
the rotation speed of the fan, and hence the air volume output of
the fan.
[0032] Outdoor unit 120 in an embodiment is a condensing unit of an
air-conditioning system or HVAC system 100. Outdoor unit 120
includes compressor 122, and as understood by those skilled in the
art, generally includes a heat exchanger with condensing coils, a
fan, valving, electrical components including a compressor
contactor, and so on. Although generally referred to an "outdoor"
unit, it will be understood that although condensing units and
other such units of an HVAC system are typically located at an
exterior of a building, such as premise 102, unit 120 could in some
embodiments be located inside premise 102. Further, it will also be
understood that while outdoor unit 120 may comprise a condensing
unit of an air-conditioning system designed for cooling, outdoor
unit 120 may also be a unit of a heat-pump or other such system,
providing heating, rather than cooling.
[0033] ERT device 114, as described further below with respect to
FIGS. 3-5, intercepts communications from temperature control
device 112 to FAU 116 and outdoor unit 120 to extend run time of
compressor 122 and circulation fan 118.
[0034] Although ERT device 114 is depicted as a stand-alone device
in FIG. 1, it will be understood that ERT device 114 may
alternatively be integrated into a temperature control device 112,
load-control switch (LCS), outdoor unit 120, or FAU 116. In one
such alternative embodiment, ERT device 114 is combined with
temperature control device such as a thermostat, such that the
present invention comprises a thermostat including ERT device 114.
In another such alternative embodiment, ERT device 114 comprises a
portion of a fan control board of FAU 116. In yet another such
alternate embodiment, ERT device 114 is integrated into an LCS.
[0035] In general operation, air is heated or cooled by
improved-efficiency HVAC system 100, and forced through a network
of air ducts by circulation fan 118. Based upon a temperature set
point at temperature control device 112, a thermostat calls for
heating or cooling based on feedback from a temperature sensor
within the conditioned space of premise 102. In the case of
cooling, the temperature control device 112 signals or requests
compressor 122 to turn on, and for circulation fan 118 to circulate
cooled air through the ductwork to various points about premise
102. When a temperature set point is reached, temperature control
device 112 ceases signaling compressor 122, and eventually fan 118,
to run. When the space temperature rises, temperature control
device 112 again calls for cool, and the process repeats.
[0036] For a single on-off cycle, the time that the compressor is
powered and actually runs will generally be referred to as the "run
time" and the time that the compressor is not powered, and
therefore not running, will generally be referred to as the "off
time".
[0037] Referring to FIG. 2, a theoretical efficiency versus run
time chart for an exemplary HVAC system is depicted. The vertical
axis of the chart represents a range of system energy efficiency
ratings (EER) ranging from "Min" for minimum efficiency to "Max"
for maximum efficiency. The horizontal axis of the chart represents
system run time in minutes. In this depicted example chart, energy
efficiency ranges from 0 to 7 EER, while time ranges from 0 to 10
minutes.
[0038] Three points, Point A, Point B, and Point C are also
depicted on the EER vs. Run Time chart of FIG. 2. At Point A, after
1 minute, the system efficiency rating is 3 EER; at Point B, after
running 5 minutes, the system efficiency has improved to 6 EER; and
at Point C, after running 9 minutes, which may be considered an
optimal amount of time, or Topt, system efficiency is maximized at
7 EER.
[0039] Although the depicted EER v. Run Time chart is only an
example of performance of a particular, theoretical HVAC system,
the chart illustrates the general concept that when a
compressor-based HVAC system begins to operate, system efficiency
may be rather low, then, after some time has passed, energy
efficiency increases non-linearly to its maximum after a period of
time.
[0040] In the chart depicted in FIG. 2, at time t=9 minutes, system
energy efficiency is maximized. Such a time is referred to as Topt.
For the portion of time that HVAC system runs beyond Topt, 9
minutes for the example depicted in the chart of FIG. 2, the system
will generally operate at maximum system efficiency.
[0041] Consequently, in an HVAC system where a compressor is
regularly cycled on and off, such as improved-efficiency HVAC
system 100 of the present invention, it is generally desirable to
size and operate the system such that the system runs for at least
a minimum run time Tmin which in some embodiments may be equal to
Topt, so as to maximize energy efficiency.
[0042] However, in an oversized system, one with excess cooling or
heating capacity, or even in a "right-sized" system when
temperatures are not extremely hot, the system may run for
significantly less time than Topt. ERT device 114 provides a
solution for improving the efficiency of such an oversized HVAC
system by increasing minimum system run time Tmin to approach
Topt.
[0043] Referring to FIG. 3, a block diagram of improved-efficiency
HVAC system 100 and ERT device 114 is depicted.
[0044] In the embodiment depicted, ERT device 114 includes power
supply 130, processor 132, memory 134, compressor time-extending
switching device 136, circulation fan time-extending switching
device 138 and call-for-cool sensing circuit 140.
[0045] Power supply 130, receives power from an external power
source, such as from FAU 116, and as understood by those skilled in
the art, conditions the power to provide an appropriate power to
processor 132 and other components of ERT device 114 as needed. In
an embodiment, power supply 130 receives a 24VAC power via the
POWER and COMMON terminals of FAU 116. In other embodiments, power
supply 130 may receive a 120VAC or other such power as is locally
available.
[0046] Processor 132 may comprise a central processing unit,
microprocessor, microcontroller, microcomputer, or other such known
computer processor. Processor 132 is in communication with memory
134, compressor time-extending switching device 136, fan
time-extending switching device 138 and call-for-cool sensing
circuit 140.
[0047] More specifically, processor 132 is in communication with
compressor time-extending switching device 136 by way of compressor
time-extending relay control line 151; with fan time-extending
relay 138 by way of fan time-extending relay control line 152; and
with call-for-cool sensing circuit 140 by way of call-for-cool
control line 154.
[0048] Memory 134, which may be a separate memory device or memory
device integrated into processor 132, may comprise various types of
volatile memory, including RAM, DRAM, SRAM, and so on, as well as
non-volatile memory, including ROM, PROM, EPROM, EEPROM, flash, and
so on. Memory 134 may store programs, software, and instructions
relating to the operation of ERT device 114.
[0049] Compressor time-extending switching device 136 comprises an
electrically operated switch, which in an embodiment comprises a
relay, which may be normally-closed single-pole, double throw relay
switch. Compressor time-extending switching device 136 may also
comprise other types of switching devices, in addition to any of
various types of known relays.
[0050] In an embodiment, compressor time-extending switching device
136 comprises a switching device of a load-control switch (LCS). As
understood by those skilled-in-the-art, an LCS is used as part of a
demand-response (DR) system of an electrical utility. An electrical
utility selectively controls power delivery to a device, such as a
compressor 122, typically by switching a device, such as a relay or
other switch, including switching device 136, on and off as needed
to shed load and reduce electrical demand. In an embodiment, ERT
114 components and/or functionality may be integrated into such an
LCS. In such an embodiment, the LCS and ERT device 114 may also
comprise a communications module for communicating with an
electrical utility 104. The communications module may include a
receiver, transmitter, antenna, memory, and so on, for data
transmission over a local and/or long-haul communications network,
such as an RF, paging, AMI, or cellular network.
[0051] In an embodiment, compressor time-extending switching device
136 includes first terminal 137a, second terminal 137b, and third
terminal 138c. First terminal 137a electrically connects to a
terminal of control circuit 150, which in an embodiment comprises a
cooling contactor. Second terminal 137b electrically connects to
control line COOL to receive the call-for-cool control signal from
temperature control device 112. Third terminal 137c is electrically
connected to a terminal or an output of power supply 130 via power
line POWER.
[0052] Compressor time-extending switching device 136 toggles
compressor control line COOL' and first terminal 137a between
second terminal 137b and call-for-cool line COOL as received from
temperature control device 112 via call-for-cool sensing circuit
140, and third terminal 137c and power line POWER as received from
FAU 116 and/or temperature control device 112. Compressor
time-extending switching device 136 receives, and is driven by, a
control signal received from processor 132 via control signal line
151.
[0053] Fan time-extending switching device 138, similar to
compressor time-extending switching device 136, comprises an
electrically operated switch, which in an embodiment comprises a
relay, such as a normally-closed single-pole, double throw relay
switch. Fan time-extending switching device 138 may also comprise
other types of switching devices, in addition to any of various
types of known relays.
[0054] In an embodiment, fan time-extending switching device 138
includes first terminal 139a, second terminal 139b, and third
terminal 139c. First terminal 139a electrically connects to
terminal FAN' of FAU 116. Second terminal 139b electrically
connects to control line FAN to receive the call-for-fan control
signal from temperature control device 112. Third terminal 139c is
electrically connected to a terminal or an output of power supply
130 via power line POWER.
[0055] Fan time-extending switching device 138 toggles first
terminal 139a and control line FAN' between second terminal 139b
and call-for-fan line FAN as received from temperature control
device 112, and third terminal 139c and a power line POWER as
received from FAU 116 and/or temperature control device 112. Fan
time-extending switching device 138 is driven by a fan control
signal received from processor 132 via control signal line 152.
[0056] In an alternate embodiment, ERT device 114 may not include a
fan time-extending switching device 138, and rather relies on
programming within temperature control device 112 to control fan
operation.
[0057] Call-for-cool sensing circuit 140 in an embodiment comprises
a trigger sense circuit, such as a Schmitt trigger. Call-for-cool
circuit 140 senses the presence or absence of a call-for-cool
control signal at line COOL as provided by temperature control
device 112. In an embodiment, call-for-cool sense circuit is a
trigger sense circuit sampling the call-for-cool control line COOL
on a periodic basis to determine whether temperature control device
112 is calling for compressor 122 to operate so as to cool premise
102. As described above, temperature control device 112 may utilize
a 24VAC control logic such that call-for-cool control line COOL
goes "high" to 24VAC when temperature control device 112 calls for
cool, and "low" or ground/common when not calling for cool.
Call-for-cool sensing circuit 140 regularly samples signal COOL
such that processor 132 can determine when temperature control
device 112 is calling for cool, i.e., for compressor 122 to
run.
[0058] As depicted in FIG. 3, compressor time-extending switching
device 136 and fan time-extending switch 138 hold switch positions
such that compressor 122 is in electrical communication with the
COOL output (call-for-cool signal) at temperature control device
112 through control circuit 150, and forced air unit 116 and its
circulation fan 118 are electrically connected to call-for-fan
terminal FAN (call-for-fan signal) at temperature control device
112. In such a configuration, ERT device 114 allows temperature
control device 112 to control compressor 122 and circulation fan
118.
[0059] Therefore, with switching devices 136 and 138 configured as
shown, in operation, when temperature control device 112 senses
that a space temperature of premise 102 has fallen below a set
point temperature, temperature control device 112 outputs a "high"
control voltage at terminals COOL and FAN, which are received,
respectively, by control circuit 150 of outdoor unit 120 and
circulation fan 118 of forced air unit 116.
[0060] Consequently, control circuit 150 upon receiving the
call-for-cool signal from temperature control device 112 switches
line voltage on to compressor 122. In an embodiment, control
circuit 150 is a contactor relay or other similar switch that
switches line voltage on and off compressor 122 based on a received
control signal, such as COOL'. The contactor may be one of many
known contactors or other known controlling devices for switching
the power of compressor 122, wherein compressor 122 may be an
air-conditioning compressor, heat pump, or other such generally
high-current-load device of a heating or cooling circuit. Control
circuit 150 may operate on alternating current (AC) or direct
current (DC), and at a control circuit voltage appropriate for the
particular control circuit, such as 24VAC.
[0061] Line voltage providing power to compressor 122 may be any of
known voltages available to compressor 122. In the United States,
in a residential application, line voltage is often 240VAC.
[0062] Although system 100 is depicted as switching compressor 122
on and off via control circuit 150, in other embodiments, other
switching configurations may be utilized. In one such alternate
embodiment, ERT device 114 outputs line voltage for use by
compressor 122.
[0063] Further, it will be understood that wherein compressor 122
provides heat for a system 100 that may comprise a heat pump,
operation is generally the same, except that a call for heat is
substituted for a call for cool.
[0064] While temperature control device 112 calls for cool via
terminal COOL, and generally for fan via terminal FAN,
call-for-cool sensing circuit 140 monitors call-for-cool line COOL
and provides data to processor 132. In an embodiment, call-for-cool
sensing circuit 140 continuously samples COOL at a predetermined
rate. In one embodiment, the sampling frequency or rate is one
sample every 1/2 second. If greater accuracy is desired, the
sampling rate may be decreased, and for lesser accuracy, the
sampling rate increased.
[0065] Processor 132 receives a signal representing call-for-cool
data from call-for-cool sensing circuit 140 at control line 154 and
determines the time period that temperature control device 112
calls for cool, or requested compressor "run time" for each on and
off cycle. As described further below with respect to FIG. 5,
processor 132 then determines whether to allow compressor 122 to be
turned off when temperature control device 112 stops calling for
cool (generally at a point when the space temperature is at or
below the desired temperature set point in the case of cooling), or
to extend the run time of compressor 122, and in some embodiments
the run time of circulation fan 118, thereby increasing efficiency
of system 100 and compressor 122.
[0066] Referring to FIG. 4, if processor 132 determines that a
requested run time of compressor 122 and/or fan 118 should be
extended, when call-for-cool signal COOL as provided by terminal
COOL of temperature control device 112 stops calling for cool,
which in an embodiment means switching from a high control voltage
of 24VAC to low control voltage, processor 132 delivers a control
signal to compressor time-extending switching device 136 via line
151, causing switching device 136 to switch.
[0067] More specifically, compressor time-extending switching
device 136 switches such that first terminal 137a no longer is
connected to second terminal 137b, but rather, is connected to
third terminal 137c. As such, call-for-cool line COOL', which
controls operation of compressor 122, switches from COOL to POWER.
Consequently, when temperature control device 112 stops calling for
cool and reduces the control voltage at COOL to low, processor 132
causes relay 136 to connect compressor call-for-cool line COOL' to
a constant logic high source, POWER. This constant logic high
source may be considered a "proxy" call-for-cool signal in that the
signal received at call-for-cool line COOL' is electrically
equivalent, or substantially similar, to the call-for-cool signal
output from temperature control device 112. The result is that
compressor 122 continues to receive a control signal indicating
that control circuit 150 should continue to power compressor 122
even after temperature control device 112 stops calling for
cool.
[0068] Similarly, processor 132 may also extend the operation of
circulation fan 118.
[0069] In most HVAC systems, a circulation fan operates for a
period of time after the compressor is turned off. During this
incremental period of time that the fan runs and the compressor
does not, air is circulated over the evaporator coils of the
system, providing some additional cooling/heating effect, and also
lowering humidity levels of the circulated air. To maintain this
"normal" operation of the fan running for a period of time after
the compressor is turned off, system 100 of the present invention
also extends operation of circulation fan 118 beyond the time that
compressor 122 is turned off.
[0070] As described above, during normal operation, temperature
control device 112 will generally call for circulation fan 118 to
operate while compressor 122 is operating. As such, when
temperature control device 112 calls for cool, it also generally
calls for fan 118 to run. If processor 132 extends operation of
compressor 122, in an embodiment, it also extends operation of
circulation fan 118. Similar to the operation of compressor
time-extending switching device 136, processor 132 provides a
control signal via fan control signal line 152 to fan
time-extending switching device 138 causing relay 138 to switch
call-for-fan control line FAN' (first terminal 139a) from FAN
(second terminal 139b) to POWER (third terminal 139c).
Consequently, even though temperature control device 112 stops
calling for fan, forced air unit 116 and its circulation fan 118
continue to receive a call for fan via fan time-extending switching
device 138.
[0071] In an embodiment, processor 132 extends the operation of
circulation fan 118 whenever processor 132 extends the operation of
compressor 122. In such an embodiment, the duration of the extended
call-for-fan time period may be equal to or greater than the
duration of the extended call-for-cool time period. In another
embodiment, operation of circulation fan 118 may be extended
independent of any extension of the operation of compressor
122.
[0072] In climates having low humidity and high heat, it may be
especially beneficial to extend operation of fan 118 to obtain
additional cooling benefits, and to remove condensate from
evaporator coils. Referring also to FIG. 2, the objective of
extending the total run time of compressor 122 and circulation fan
118 is to operate these components of improved-efficiency HVAC
system 100 for a period of time that improves system efficiency.
For example, if HVAC system 100 was operating at point A on the
chart of FIG. 2 (Run Time of 1 minute and EER of 3), perhaps due to
oversizing of the system, ERT device 114 may cause a minimum run
time Tmin of system 100, by way of compressor 122 and generally fan
118, to be increased such that system 100 operates at Point B
(minimum run time of 5 minutes, EER of 6) or at Point C (minimum
run time of 9 minutes, which is equal to Topt, EER at maximum of
7).
[0073] As described further below, ERT device 114 may increase or
extend run time to force system 100 to operate at maximum
efficiency, for example, at Point C, or at other points less than
maximum efficiency, for example, Point B. Such an extension of the
run time may be brought about by gradual increases in run time
until a desire run time is achieved. Further, if ERT device 114
detects that temperature control device 112 already is operating
for a period of time as requested by temperature control device 112
and above a minimum run time, such as Topt, ERT device 114 may not
extend the run time further.
[0074] In an embodiment, minimum run time, Tmin, is simply the
predetermined total amount of time that compressor 122 and HVAC
system 100 needs to run in a single on/off cycle in order to
operate at maximum system efficiency. In another embodiment,
minimum run time is less than the amount of time that compressor
122 and HVAC system 100 needs to run in order to operate at maximum
system efficiency. In other words, for a single cycle, compressor
122 runs for a period of time that is less than that which would
result in optimum efficiency, but still improves system
efficiency.
[0075] Referring to FIG. 5, a flowchart depicting the steps for
determining and implementing an extended system run time is
depicted. More specifically, the flowchart of FIG. 5 depicts the
steps for extending system run time for a cooling system over a
single operating cycle (one run time period followed by an off time
period). It will be understood that these steps may also apply to a
heating system. In such a method, a "call for heat" control signal,
rather than a call for cool control signal may be implemented, with
temperature control device 112 calling for heat when a space
temperature falls below a predetermined set point, rather than
above.
[0076] At step 170, temperature control device 112 monitors a space
temperature of premise 102.
[0077] At step 172, if a measured space temperature is above a
predetermined temperature set point, at step 174, temperature
control device 112 outputs a call-for-cool control signal. It will
be understood that temperature control device 112 may be programmed
or otherwise configured to allow a space temperature to rise by a
predetermined amount above the desired temperature set point so as
to prevent frequent cycling of HVAC system 100. For example,
despite a temperature set point of 72.degree. F., the space
temperature may be allowed to rise to 72.5.degree. F. or 73.degree.
F., before temperature control device 112 calls for cool.
[0078] At step 172, if the measured space temperature is at or
below the predetermined temperature set point, temperature control
device 112 continues to monitor the space temperature at step
170.
[0079] At step 174, temperature control device 112 outputs a
call-for-cool control signal. Referring also to FIG. 3, in an
embodiment, temperature control device 112 outputs a 24VAC control
signal (call-for-cool control signal) at terminal COOL of
temperature control device 112, which is received by ERT device 114
at call-for-cool sensing circuit 140. Alternatively, in an HVAC
system 100 that provided heat via compressor 122, temperature
control device 112 would similarly output a call-for-heat control
signal which would be received by a call-for-heat sensing circuit
140 of ERT device 114.
[0080] In an embodiment, temperature control device 112 also
outputs a call-for-fan control signal. One such embodiment is
depicted in FIG. 3, wherein temperature control device 112 outputs
a call-for-fan control signal of 24VAC at terminal FAN, which is
then received by ERT device 114 at fan time-extending switching
device 138, and conveyed to FAU 116.
[0081] At step 176, and as described above with respect to FIG. 3,
the call-for-cool control signal results in power being applied to
compressor 122, such that compressor 122 begins to run. In an
embodiment such as one depicted in FIG. 3, the call for cool is
conveyed to control circuit 150, which causes a relay within
control circuit 150 to connect line voltage to compressor 122,
causing it to begin running.
[0082] Further, the call-for-fan control signal is received at FAU
116, which causes circulation fan 118 to begin to operate, and
circulate air cooled by compressor 122 through system 100.
[0083] At step 178, ERT device 114 monitors the call-for-cool
control signal output by temperature control device 112. In an
embodiment, call-for-cool sensing circuit 140 samples the
call-for-cool signal output to determine whether the call-for-cool
control signal is "high" or "low", or in other words, whether
temperature control device 112 is calling for cool. In one such
embodiment, and as described above, call-for-cool sense circuit
samples the voltage at signal line COOL (equivalent to terminal
COOL of temperature control device 112) at a predetermined
frequency. Call-for-cool sensing circuit 140 transmits over line
154 sampled data or data representative of the sampled data to
processor 132.
[0084] Processor 132 receives the sampled data representing the
call-for-cool control signal. Processor 132 uses the call-for-cool
control signal data to determine how long temperature control
device 112 has been calling or requesting cool, and hence how long
compressor 122 has been running. Such a calculation may be
calculated and updated continuously such that a new compressor run
time is calculated with each new data sample received, or a single
compressor run time may be calculated when temperature control
device 112 ceases to call for cool.
[0085] At step 180, temperature control device 112 ceases to call
for cool. Generally, this is a result of a space temperature
reaching a desired temperature set point, such compressor 122 would
normally be turned off.
[0086] At step 182, temperature control device 112 determines the
period of time that temperature control device 112 was calling for
cool, the requested compressor run time T.sub.REQ. For example, if
temperature control device 112 called for cool such that
call-for-cool control signal line COOL was at 24VAC for 5 minutes,
then stopped calling for cool such that COOL dropped to 0VAC,
processor 132 would determine based upon sampled data received from
call-for-cool sensing circuit 140, that requested compressor run
time T.sub.REQ was 5 minutes.
[0087] In an embodiment, a single occurrence of a change in control
voltage from high to low at signal line COOL will identify an end
of the time period T.sub.REQ. In another embodiment, a change in
control voltage must be sustained for a minimum period of time, or
sampling periods.
[0088] After determining the requested compressor run time
T.sub.REQ at step 182, processor 132 compares T.sub.REQ to a
predetermined desired run time T.sub.MIN at step 184. If T.sub.REQ
is not less than a predetermined desired run time T.sub.MIN, i.e.,
is equal to or greater than T.sub.MIN, power is removed from
compressor 122 at step 188, and temperature control device 112
continues to monitor the space temperature of premise 102 at step
170. In such a condition, namely, when T.sub.REQ is equal to or
greater than T.sub.MIN, compressor 122 and system 100 is operating
at a sufficient efficiency level such that no intervention in the
form of an extended run time, is required.
[0089] If at step 184 processor 132 determines that T.sub.REQ is
less than a predetermined desired run time T.sub.MIN, then control
of compressor 122 and fan 118 is switched over to ERT device 114 at
step 186.
[0090] At step 190 power to compressor 122 and fan 118 is
maintained, causing compressor 122 and fan 118 to continue running,
thereby extending the run time of compressor 122 and fan 118. The
additional run time above the requested run time T.sub.REQ is
defined as extended run time T.sub.EXT, such that a total run time
T.sub.TOT is the sum of T.sub.REQ and T.sub.EXT. Generally,
T.sub.TOT will be equal to T.sub.MIN.
[0091] The additional extended run time T.sub.EXT may be different
for compressor 122 and fan 118. In an embodiment, fan 118 continues
to run after power is removed from compressor 122. In such an
embodiment, fan 118 T.sub.EXT is greater than compressor 122
T.sub.EXT. Extending the run time for either compressor 122 or fan
118 is described above with respect to FIGS. 3 and 4.
[0092] At step 192, at the end of the extended run time period
T.sub.EXT, control of compressor 122 and fan 118 is returned to
temperature control device 112. As described above with respect to
FIGS. 3 and 4, in an embodiment, this step is accomplished when
processor 132 causes compressor time-extending switching device 136
to connect compressor control line COOL' to temperature control
device 112 output COOL, and when processor 132 causes fan
time-extending switching device 138 to connect control line FAN' to
temperature control device 112 output FAN. In such an embodiment,
temperature control device 112 then controls operation of
compressor 122 and circulation fan 118.
[0093] In the case of a cooling system 100, when control is turned
over to temperature control device 112 at the end of the extend run
time period T.sub.EXT, temperature control device 112 will
generally not be calling for cool or fan because compressor 122 and
fan 118 have been operating. In such a case, a control voltage at
COOL' and FAN', as output from temperature control device 112, will
be low, and power to compressor 122 and fan 118 will be
removed.
[0094] Subsequently, temperature control device 112 will continue
to monitor the space temperature of premise 102 at step 170, and
the cycle begins again.
[0095] With respect to the duration of extended time period
T.sub.EXT, in an embodiment, T.sub.EXT is simply as follows:
T.sub.EXT=T.sub.MIN-T.sub.REQ EQN 1:
[0096] In such an embodiment, processor 132 dynamically determines
T.sub.EXT based on the previous operating cycle, or a combination
of previous operating cycles, such that compressor 122 and/or fan
118 always runs for at least the predetermined minimum time period
T.sub.MIN. As described above, T.sub.MIN may be selected based on
an overall desired efficiency of system 100, or compressor 122. If
optimum efficiency is desired, T.sub.MIN will generally be equal to
T.sub.OPT.
[0097] Referring again to FIG. 2, in an embodiment, an HVAC system
100 has a maximum energy efficiency rating of 7 at a run time equal
9 minutes. The run time of 9 minutes is defined as the optimal run
time T.sub.OPT. If system 100 is oversized with respect to premise
102 such that system 100 and compressor 122 generally run less than
the optimal run time T.sub.OPT of 9 minutes, then the run time is
extended using ERT device 114.
[0098] In such an embodiment, a predetermined minimum run time
T.sub.MIN may be set equal to T.sub.OPT, or 9 minutes, such that
system 100 operates at Point C as depicted in FIG. 2.
Alternatively, T.sub.MIN may be set to another run time less than
T.sub.OPT, which in an embodiment is 5 minutes, corresponding to
Point B in FIG. 2, and having an EER of 6. As such, T.sub.MIN may
be a predetermined time period that causes compressor 122 to
operate anywhere along the EER vs. run time curve, thusly improving
the efficiency of system 100 and compressor 122 in any
increment.
[0099] Forcing compressor 122 and circulation fan 118 to operate
longer than requested by temperature control device 112 not only
improves system 100 efficiency, but also improves humidity control
and air mixing by allowing fan 118 to operate for longer periods of
time.
[0100] However, extending the run time of compressor 122 and
circulation fan 118 to achieve improved efficiency may cause a
space temperature of premise 102 to fall below (cooling) or rise
above (heating) a desired temperature set point. Generally, the
greater the extended run time T.sub.EXT as compared to the
requested run time T.sub.REQ, the greater the variation in
temperature below or above the desired temperature set point. Such
temperature variations may become noticeable to a person within
premise 102.
[0101] To illustrate this relationship, referring again to FIGS. 1
and 2, in an embodiment, an oversized system 100 operates without
an ERT device 114 at Point A, such that temperature control device
112 request that compressor 122 run for only 1 minute every cycle
in order to hold a desired temperature set point at a space of
premise 102. System 100 efficiency may be improved by extending
compressor 122 run time by T.sub.EXT to move operation of system
100 along the curve depicted in FIG. 2. If T.sub.MIN is set to 9
minutes for maximum system efficiency, T.sub.EXT is equal to 8
minutes, causing compressor 122 to run for 9 minutes total, rather
than 1 minute.
[0102] However, temperature control device 112 requested a 1 minute
run time based on the amount of time needed, or cool air volume
needed, to cool premise 102 to the desired temperature set point.
If system 100 continues to operate for 8 minutes beyond what is
required to meet the temperature set point needs, a space
temperature of premise 102 will fall well below the desired
temperature set point. Some persons may find such temperature
swings noticeable and uncomfortable.
[0103] One solution is to set a minimum run time T.sub.MIN to be
less than an optimal run time T.sub.OPT. T.sub.EXT is still
determined based on EQN. 1 above, but will have a shorter duration
when T.sub.MIN is less than T.sub.OPT.
[0104] In an embodiment, a user or on-site technician initially
sets T.sub.MIN to be at T.sub.OPT, then adjusts T.sub.MIN downward
until temperature variations resulting from system 100 turning on
and off are acceptable based on user perception.
[0105] In another embodiment, other criteria may be used to
manually or automatically determine either a minimum run time
T.sub.MIN or an extended run time T.sub.EXT. In one such
embodiment, T.sub.EXT may be defined as a multiple of T.sub.REQ as
follows:
T.sub.EXT=M.times.T.sub.REQ, EQN 2:
Wherein "M" is predetermined multiplier used to determine
T.sub.EXT.
[0106] Alternatively, T.sub.EXT may be capped such that T.sub.TOT
does not exceed T.sub.OPT, so as to maximize efficiency, but
minimize temperature variation in premise 102. In such an
embodiment, T.sub.EXT may be defined by the following two
equations:
T.sub.EXT=Min(M.times.T.sub.REQ,T.sub.OPT-T.sub.REQ) for
T.sub.REQ<T.sub.OPT EQN. 3:
and
T.sub.EXT=0 for T.sub.REQ.gtoreq.T.sub.OPT EQN. 4:
[0107] Theoretical exemplary run time data of an embodiment of
system 100 with ERT 114 and having a fixed multiplier M and
T.sub.EXT calculated per EQNS. 3 and 4, is described in Table 1
below, with all run times in minutes, and based on the exemplary
efficiency curve depicted in FIG. 2:
TABLE-US-00001 TABLE 1 Optimal Requested Efficiency Extended Total
Run Run Time Run Time Initial Multiplier Run Time Time Improved
(T.sub.REQ) (T.sub.OPT) EER (M) (T.sub.EXT) (T.sub.TOT = T.sub.REQ
+ T.sub.EXT) EER 1 9 3 0.5 0.5 1.5 3.5 3 9 4.7 0.5 1.5 4.5 5.5 5 9
6 0.5 2.5 7.5 6.5 7 9 6.4 0.5 2 9 7 9 9 7 0.5 0 9 7 12 9 7 0.5 0 12
7
[0108] Table 1 may characterize a range of requested run times
T.sub.REQ for a single system 100 or compressor 122, that vary with
cooling or heating loads. In the embodiment of system 100 with ERT
114 characterized by the theoretical data of Table 1, multiplier M
is held constant at 0.5. In such an embodiment, requested run time
for a system 100 may change as depicted in Table 1, ranging from 1
minute to 12 minutes. Multiplier M is held constant, regardless of
run time. T.sub.EXT is determined by processor 132 according to
EQNS. 3 and 4. Total run time T.sub.TOT is increased as shown, and
system efficiencies improved.
[0109] In an alternate embodiment, multiplier M may be dynamically
determined by processor 132 based on measured requested run time
T.sub.REQ. In one such embodiment, multiplier M varies inversely to
requested run time T.sub.REQ. In such an embodiment, M is generally
larger for shorter requested run times T.sub.REQ, and smaller for
longer requested run times T.sub.REQ. Multiplier M may be
associated with a particular range of requested run times
T.sub.REQ, such as M=2 for requested run times T.sub.REQ that are
less than 3 minutes; M=1 for requested run times T.sub.REQ that are
equal to or greater than 3 minutes, but less than 5 minutes, and so
on. Such an embodiment provides the benefit of increasing total run
times T.sub.TOT for particularly low requested run times
T.sub.REQ.
[0110] Theoretical exemplary run time data of an embodiment of
system 100 with ERT 114 and having a dynamic multiplier M and
T.sub.EXT calculated per EQNS. 3 and 4, is described in Table 2
below, with all run times in minutes, and based on the exemplary
efficiency curve depicted in FIG. 2:
TABLE-US-00002 TABLE 2 Optimal Requested Efficiency Extended Total
Run Run Time Run Time Multiplier Initial Run Time Time Improved
(T.sub.REQ) (T.sub.OPT) (M) EER (T.sub.EXT) (T.sub.TOT = T.sub.REQ
+ T.sub.EXT) EER 1 9 2 3 2 3 4.7 3 9 1 4.7 3 6 6.4 5 9 0.5 6 2.5
7.5 6.6 7 9 0.5 6.4 2 9 7 9 9 0.5 7 0 9 7 12 9 0.5 7 0 12 7
[0111] As depicted in Table 2, multiplier M varies inversely with
requested run time T.sub.REQ. At a requested run time T.sub.REQ of
1 minute, multiplier M is relatively large at M=2, so as to provide
a relatively larger extended run time T.sub.EXT. Multiplier M
decreases as requested run time T.sub.REQ approaches T.sub.OPT.
[0112] It will be understood that other embodiments of the present
invention may include alternate algorithms for determining extended
run time T.sub.EXT and multiplier M, based upon the principles of
extending compressor run time so as to increase efficiency, with
minimal temperature variation and possible discomfort at a premise
102.
[0113] Although the present invention has been described with
respect to the various embodiments, it will be understood that
numerous insubstantial changes in configuration, arrangement or
appearance of the elements of the present invention can be made
without departing from the intended scope of the present invention.
Accordingly, it is intended that the scope of the present invention
be determined by the claims as set forth.
[0114] For purposes of interpreting the claims for the present
invention, it is expressly intended that the provisions of Section
112, sixth paragraph of 35 U.S.C. are not to be invoked unless the
specific terms "means for" or "step for" are recited in a
claim.
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